Although venemous snakes have a place in nature's scheme, their presence in close proximity to human habitations is frequently not desired. In some instances, encounters are dangerous, and even fatal, and where poisonous snakes are known to be present, most human beings feel uneasy and must perform even commonplace chores, such as gathering wood from the woodpile, with considerable caution and some degree of trepidation.
Most people, particularly farmers and ranchers, welcome the presence of non-venemous snakes for their help in keeping the rodent population in check; and, fortunately, most snakes are of this kind. The family Colubridae, represented by such familiar snakes as blacksnakes and garter snakes, contains nearly two thirds of the known species of snakes.
In the continental United States, however, there are four species of poisonous snakes. One of these is the coral snake, a snake which is seclusive and inoffensive and is really only dangerous when being handled.
The other three species of venomous snakes are the rattlesnake, the water moccasin (or cottonmouth) and the copperhead. These snakes are all pit vipers of the family Cotalidae. In addition to having a deep pit (hence the name pit viper) between the eyes and nostrils, pit vipers are distinguished by a flattened, triangular head. That is, the head is distinctly wider than the neck so that, speaking in mechanical or structural terms, the base of the triangular head protrudes transversely from opposite sides of the neck to provide, as it were, a pair of transversely projecting shoulders.
It is this unique characteristic on which the present trap relies to perform its function. Since only pit vipers possess this head configuration and since all pit vipers are venomous, only dangerous snakes are captured by the trap.